It's not so much that they seem trained, or that they're familiar with one another, but they act a bit like a pack of dogs. It's sort of an instinctual knowledge of how to work together when it's called for. But then, they also communicate now and then in their tonal, musical language, so it's safe to assume they're collaborating in more meaningful ways as well.
Each spirit is an individual. Some may look sort of similar; there could be a group of them that look like weird hairy things with horns, for example. But there would be differences between them in terms of height, color, horn shape, etc.. The green-eyed spirits don't all look like the image given, either. Individual spirits will be described in more detail in threads.
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